Electronic control system for magnetic valves operated individually or in cascade

ABSTRACT

An electronic control system for individually operated magnetic valves and valve cascades automatically switches to individual operation or cascade operation by a switching logic. The switching logic detects the presence of an actual value signal of a main valve of a valve cascade so that the electronic control system is automatically adjusted to cascade operation in this case. In the absence of an actual value of the main valve, a cable interruption is detected and the final stage is locked. At-14 Volts at the main stage actual value input, the electronic control system is adjusted to the individual operation of a magnetic valve.

BACKGROUND OF THE INVENTION

The invention concerns an electronic control system for magnetic valveswhich are operated individually or in cascade.

Different drives can be used for the actuation of valves. Valves can beprovided with a magnet drive for controlling low outputs, while higheroutputs require a hydraulic drive. Accordingly, with lower outputrequirements a magnetic valve operated individually can be electricallyadjusted by means of a regulator. With higher output requirements amagnetic valve is connected upstream of a hydraulically actuated mainvalve and the pressure medium for actuating the main valve is controlledvia the magnetic valve. Together with the main valve, the magnetic valveforms a valve cascade in which the magnetic valve is operated as a pilotvalve. The regulating voltage put out by the regulator does not actdirectly on the main valve which is actually to be adjusted, but ratheris applied to the controlling magnet of the magnetic valve. A regulatingvoltage can be derived from a comparison between the reference value andactual value of the position of the main valve, which regulating voltagecontrols the magnetic valve connected upstream in such a way that thevalve position of the main valve is adjusted to the reference value.

The electronic control system used to generate the regulating voltage isusually accommodated in a control unit arranged separately from thevalves. Depending on the type of valve--individually operated magneticvalve or valve cascade including pilot valve and main valve--differentcircuit arrangements are used for the two different types of control.This has the disadvantage that the construction of the electroniccontrol system must be adapted to the respective operating type -individual operation or pilot operation.

SUMMARY OF THE INVENTION

Accordingly, it is an object of the present invention to provide anelectronic control system of the above mentioned type, which avoids thedisadvantages of the prior art.

In keeping with these objects and with others which will become apparenthereinafter, one feature of the present invention resides, brieflystated, in an electronic control system for individually operatedmagnetic valves and for valve cascades with a magnetic valve operated asa pilot valve which controls a main valve acted upon by a pressuremedium, a regulator generating the regulating voltage for the magneticvalve, characterized in that a signal input for the actual valve of thevalve position of the main valve is connected with a switching logicwhich adjusts the electronic control system to individual operation whena constant level characterizing the individual operation is present atthe control input or adjusts the electronic control system to pilotoperation when the actual value of the valve position of the main valveis present at the control input, a regulator derives the regulatingvoltage from a comparison of the reference value with the actual valueof the magnetic valve in individual operation and from a comparison ofthe reference value and actual value of the main valve in pilotoperation.

When the electronic control system is designed in accordance with thepresent invention, it has the advantage over the prior art that aswitching logic automatically adjusts the control from individualoperation or pilot operation depending on the utilized valves. To thisend the switching logic detects whether or not an actual value of a mainvalve is present at the control input provided for this purpose. If thevalve to be controlled is an individually operated magnetic valve thereis compulsorily no corresponding actual value at the signal input forthe main valve, rather a constant level is applied to this controlinput. This constant level is detected by the switching logic and theelectronic control system is thereupon switched to individual operation.If the electric line to the d.c. voltage source supplying theaforementioned constant level is interrupted, this disturbance isdetected by the switching logic which can then trigger an errordetection, an alarm signal or the like. The electronic control systemcan be mounted directly on magnetic valves regardless of whether or notthese magnetic valves are subsequently used in individual operation orin pilot operation in connection with main valves. This universalapplicability of the electronic control system makes it possible tostreamline manufacture and storage.

In pilot operation with the main valve being acted upon by a pressuremedium, a first differential amplifier and a second differentialamplifier connected downstream of the latter are active in theelectronic control system. The first differential amplifier compares thereference value and actual value of the main valve and the seconddifferential amplifier compares the output of the first differentialamplifier with the actual value of the magnetic valve and supplies theregulating voltage for the magnetic valve on its output side. On theother hand, in individual operation only the second differentialamplifier is active and compares the reference and actual values of themagnetic valve. Thus, the electronic control system is provided withcircuit elements for individual operation and pilot operation which arenot fully discrete. Rather, the second differential amplifier, forexample, is used in individual operation as well as in pilot operationfor generating the regulating voltage. This has the advantage not onlythat the expenditure on circuitry for the electronic control system islow, but also that the output end stage which is controlled by theregulating voltage and connected on the output side with the magnet ofthe magnetic valve is connected with the output of the seconddifferential amplifier in every type of operation. Accordingly, only oneregulating voltage output is required for both types of operation.

The electronic control system can further include an actual value outputat which the actual value of the valve position of the main valve orindividually operated magnetic valve can be taken off. To this end thecorresponding actual value inputs are switched through to the actualvalue output via alternately closed switches. The switching is carriedout by the same switching logic which carries out the switching betweenindividual operation and pilot operation. The total circuit cost isaccordingly kept relatively low.

To enable reliable detection of the respective desired type of operationfor the switching logic, a defined d.c. voltage can be applied to thecontrol input connected with the switching logic in individual operationby means of a contact bridge. The d.c. voltage value of this d.c.voltage lies outside the possible actual value range of the main valveso as to enable an unequivocal detection of the respective desired typeof operation for the switching logic. If the contact bridge orconnection to a connected actual value transmitter is interrupted, thiserror state can be detected and indicated by the switching logic.

The novel features which are considered as characteristic for theinvention are set forth in particular in the appended claims. Theinvention itself, however, both as to its construction and its method ofoperation, together with additional objects and advantages thereof, willbe best understood from the following description of specificembodiments when read in connection with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The single FIGURE of the drawings is a view schematically showing anelectronic control system for individually operated magnetic valves andfor valve cascades, in accordance with the present invention.

DESCRIPTION OF PREFERRED EMBODIMENTS

The drawing shows an electronic control system for individually operatedmagnetic valves and for valve cascades with a magnetic valve operated asa pilot valve. The actual value S (IH) of the valve position of a mainvalve, not shown, is received from an actual value transmitter 1 whichdetermines the actual valve position as path s, transforms it into anelectrical actual value U (IH) and supplies it to a control input SE1 ofthe electronic control system. If the electronic control system is usedfor controlling an individually operated magnetic valve, the controlinput SE1 is not connected with the actual value transmitter 1, butrather is applied at a constant level of -14V via a contact bridge 2.

The control input SE1 is connected in the electronic control system withthe input of a switching logic 3 and with the first input of a firstdifferential amplifier V1. The reference value U (S) of a given valveposition is present at the second input of the differential amplifierV1. The reference value U (S) can be modified by a signal transformer 4.The signal transformer 4 can adapt e.g. the offset and the level rangeof the reference value to the actual value U (IH).

The reference value U (S) is supplied not only to the second input ofthe first differential amplifier V1 via the signal transformer 4 but isalso present at the input of an inverter I1. The first differentialamplifier V1 and the inverter I1 can be connected on the output side viaassociated switches S1 and S2 with a first input of a seconddifferential amplifier V2. The actual value U (ISP) representing thevalve position of a magnetic valve operated as an individual valve orpilot valve is applied to the second input of the second differentialamplifier V2. The valve position S (ISP) is picked up by an actual valuetransmitter 5 as path s and transformed into a voltage U as electricalactual value U (ISP).

The output of the second differential amplifier V2 supplies theregulating voltage U (R) to the regulating voltage output RA. Thedifferential amplifiers V1, V2 and the inverter Il form a regulator Rwhich generates the regulating voltage U (R) as a function of presentactual values and reference values.

The switching logic 3 has a first output Q and an inverse output Q whichare connected with actuating magnets Ml and M2, respectively, orelectronic switching inputs or electronic switches. If the level -14V isapplied to the input of the switching logic 3, the switching logic 3activates the output Q so that the actuating magnet Ml or electronicswitch closes the switches S2 and S4 connected with it. The inverseoutput Q is not activated in this case so that the actuating magnet M2or electronic switches allow the switches S1 and S3 associated with itto be opened. On the other hand, if the actual value U (IH) of the mainvalve is applied to the control input SE1 this state is detected by theswitching logic 3 and the output Q and the actuating magnet M2 orelectronic switch connected thereto is activated. As a result, theswitches S1 and S3 are closed while the switches S2 and S4 remain open.

1. Individually operated magnetic valve

The switches S2 and S4 are closed, while the switches S1 and S3 areopen. The reference value U (S) is supplied via the inverter I1 and theswitch S2 to the first input of the second differential amplifier V2,the actual value U (ISP) of the individually operated magnetic valvebeing applied to its other input. The actual value U (ISP) is alsosupplied to the actual value output IA via the switch S4. The regulatingvoltage U (R) required to regulate the magnetic valve occurs at theoutput of the second differential amplifier V2.

Since the switch S1 is open, the first differential amplifier V1 isinactive.

2. Pilot operation of the magnetic valve for controlling a main valveacted upon by a pressure medium

The actual value U (IH) of the main valve is applied to the controlinput SE1. The switches S1 and S3 are closed while the switches S2 andS4 are open. A comparison of the actual value U (IH) with the modifiedreference value U (S) is carried out at the first differential amplifierV1 and a corresponding control voltage which is applied to the firstinput of the second differential amplifier V2 is generated at the outputof the first differential amplifier V1. The actual value U (ISP) of themagnetic valve whose position is adjusted by the regulating voltage U(R) provided at the second differential amplifier V2 is applied to thesecond input of the second differential amplifier V2.

The inverter I1 is inactive in this case due to the open switch S2. Theactual value U (IH) of the main valve is applied to the actual valueoutput IA.

It will be understood that each of the elements described above, or twoor more together, may also find a useful application in other types ofconstructions differing from the types described above.

While the invention has been illustrated and described as embodied in anelectronic control system for individually operated magnetic valves andfor valve cascades, it is not intended to be limited to the detailsshown, since various modifications and structural changes may be madewithout departing in any way from the spirit of the present invention.

Without further analysis, the foregoing will so fully reveal the gist ofthe present invention that others can, by applying current knowledge,readily adapt it for various applications without omitting featuresthat, from the standpoint of prior art, fairly constitute essentiallycharacteristics of the generic or specific aspects of this invention.

What is claimed as new and desired to be protected by Letters Patent isset forth int he appended claims.
 1. An electronic control system forindividually operated magnetic valves and for valve cascades with amagnetic valve operated as a pilot valve which controls a main valveacted upon by a pressure medium, the electronic control systemcomprising a regulator generating a regulating voltage for a magneticvalve; a signal input for an actual value of a valve position of a mainvalve; a switching logic which adjusts the electronic control system toindividual operation when a constant level characterizing the individualoperation is present at the signal input or adjusts the electroniccontrol system to pilot operation when an actual value of a valveposition of the main valve is present at the signal input, saidregulator deriving the regulating voltage from a comparison of areference value with the actual value of the magnetic valve inindividual operation and from a comparison of the reference value andthe actual value of the main valve in pilot operation.
 2. An electroniccontrol system as defined in claim 1; and further comprising first andsecond differential amplifiers, an inverter, and two switches, saidsignal input for the actual value of the main valve being connected withan input of said switching logic and a first input of said firstdifferential amplifier, the reference value of valve position of themain valve or of the magnetic valve in individual operation beingpresent at a second input of said first differential amplifier and at aninput of said inverter, two outputs of said first differential amplifierand of said inverter being connected with a first input of said seconddifferential amplifier via said switches which can be actuated in anopposite direction by said switching logic, the actual value of thevalve position of the magnetic valve operated as individual valve orpilot valve being present at a second input of said second differentialamplifier whose output supplies the regulating voltage.
 3. An electroniccontrol system as defined in claim 2; and further comprising a thirdswitch and a fourth switch, the signal input for the actual value of themain valve being connectable with an actual value output via said thirdswitch or an input for the actual value of the magnetic valve isconnectable with an actual value output via said fourth switch.
 4. Anelectronic control system as defined in claim 1; and further comprisinga contact bridge, said signal input being electrically connected with ad.c. voltage source via said contact bridge during individual operationof a magnetic valve.